• show
  • Since the general criterion in Bargmann's theorem was not known when Wigner did his classification, he needed to show by hand (Section 5 of the paper) that the phases can be chosen in the operators to reflect the composition law in the group, up to a sign, which is then accounted for by passing the to double cover of the PoincarĂ© group. (wikipedia.org)
  • general
  • Classification is a general process related to categorization, the process in which ideas and objects are recognized, differentiated, and understood. (wikipedia.org)
  • In typography, the Thibaudeau Classification is a way to group typefaces into four general families, according to shape and serif character. (wikipedia.org)